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Walter Roberson


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48,720 total contributions since 2011

I do not do free private consulting. If you want to bring my attention to something, send a link to the MATLAB Answers location.

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Answered
How do I efficiently iterate over subvectors of a given vector?
https://www.mathworks.com/help/matlab/ref/movsum.html

9 hours ago | 1

| accepted

Answered
How to read all .csv files from a folder in an order?
https://www.mathworks.com/matlabcentral/fileexchange/47434-natural-order-filename-sort

9 hours ago | 1

Answered
How to correlate spectral coeficient
Calculation of spectral coefficients is almost always done over a particular number of samples (representing a pre-determined am...

18 hours ago | 0

Answered
Smooth function not working
which smooth You will find that you are using some other smooth function, not toolbox/curvefit/curvefit/smooth.m . In the offic...

18 hours ago | 0

Answered
How to create combinations of rows in an array?
result = permute(reshape( data(perms(1:size(data,1)).',:).', size(data,2), size(data,1), []), [2 1 3]);

18 hours ago | 0

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Answered
Introducing new rows (or columns) into an existing matrix with interpolated values to fill technically non-existent gaps.
Create a timetable() object and use retime() https://www.mathworks.com/help/releases/R2017a/matlab/ref/retime.html

20 hours ago | 0

Answered
syntax errors symbolic to logical
You missed the point that requires that the gradient of f be evaluated at x. You are taking the symbolic gradient of f into gf,...

20 hours ago | 0

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Answered
How can i create constant in a .m archive and use it for the creation of new objects?
https://www.mathworks.com/help/matlab/matlab_oop/properties-with-constant-values.html and note https://www.mathworks.com/help/ma...

21 hours ago | 1

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Answered
whats problem in my code for solve newton Rhapson method for equation 4-x^2-y^2 1-exp(x)-y
Suppose we could find some way to make your assignments to f(x,y) and g(x,y) work out. Then what would you do with the results? ...

22 hours ago | 0

Answered
How do I label pcolor y and x axes please
img = sort(randi([0 255], 240, 320, 'uint8')); subplot(1,2,1); imagesc(img); colormap(hot); xlabel('x'); ylabel('y'); subplot(...

22 hours ago | 0

Answered
How to perform these discrete signals?
is the Dirac delta function. dirac(x) is zero whenever x is not zero, and has a non-zero value when x is 0. Call that value D. ...

22 hours ago | 0

Answered
How to set bounds on fmincon manually
x0(1,:) = (x1_bounds(1,2)-x1_bounds(1,1)).*rand(1,SearchPoints) + x1_bounds(1,1); x0(2,:) = (x2_bounds(1,2)-x2_bounds(1...

23 hours ago | 0

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Answered
Fimplicit not plotting properly
a=2; h=0/2; b=0; g=3/2; f=1/2; c=7; fun1=@(x,y) a.*x.^2+2*h.*x.*y+b*y.^2+2*g.*x+2*f.*y+c; fimplicit(fun1, [-10 10 -10 10]) Lo...

1 day ago | 1

Answered
How to do a rem while loop?
while true h = input('Enter the desired grid spacing: '); if isnumeric(h) && isscalar(h) && h > 0 && rem(h,1) == 0; br...

1 day ago | 0

Answered
Laplace transform not found.
The wk^3*exp(x*tau) is getting integrated to include a /tau^4 term -- the general pattern wk^n*exp(...*tau) integrates to someth...

1 day ago | 0

Answered
matlab error ode45
x0=[0,10,45]; %initial condtion tspan=[0,30];% time span u=10; odefun = @(t,y)reshape(rolling(t,y,u), [], 1); [t,x]=ode45(...

1 day ago | 0

Answered
vpasolve -> Empty sym: 0-by-1
I was seeing some oddities when I solved, so I tried solving two different ways: R=8.3144; T=298.15; F=96487; eps0= 8.854*10...

1 day ago | 0

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Answered
What does [3, Inf] represents?
In addition to what the others say: that kind of variable would tend to be used as the size parameter for reading data, such as ...

2 days ago | 1

| accepted

Answered
For loop stores all zeros then the actual values of last iteration
Your statement finalsm = zeros(height(x),1); % 'height(x)' bc array changes size each iteration is throwing away all previ...

2 days ago | 0

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Answered
convert binary string into hex
lookup = containers.Map(cellstr(dec2bin(0:15,4)),cellstr(dec2hex(0:15))); binary_string = '0101010011101010'; output = cel...

2 days ago | 0

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Answered
How to read text file backwards?
You can fopen() the file for reading and fseek() to a particular offset relative to the end of file. You will not be able to fs...

2 days ago | 0

Answered
ERROR Subscript indices must either be real positive integers or logicals.
for j=1:j_max+1 x=v((j-1:j+N0-2)*dt); j starts at 1. j-1 starts at 0. 0 multiplied by anything is 0. Therefore your first ind...

2 days ago | 0

Answered
Why do the lines not plot to completion
solution2=ode45(vector2, [0 1], [.39 0]); factor2=((1+b_2)/(F))*(solution2.y(2,:)); % Effective Factor First Order 1 so fact...

2 days ago | 1

Answered
How Can I Pull A Specific Variable From The Determinant of Matrix?
You have no realistic chance of calculating one variable in terms of the other symbolically. Your function involves the first tw...

2 days ago | 0

Answered
How to combine the using of meshgrid and surface?
x = linspace(0,.1); y = linspace(.3, .4); [X, Y] = meshgrid(x, y); Z = X.^2 - 5.*Y.^3 + sin(5*2*pi*X); surf(X, Y, Z, 'edgeco...

3 days ago | 0

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Answered
Get rid of unnecessary space in output of full(A)
disp(num2str(full(A))) You can add a format specifier to num2str() to be more specific about widths.

3 days ago | 1

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Answered
Merge data by date
Convert your data to a timetable() object, and use retime() to consolidate the information.

3 days ago | 0

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Answered
Can I pcolor base on wavelength, any colormap can do so?
When you pcolor(X,Y,I) then the I data will be used to decide which color information is used. By default, the numerically lowes...

3 days ago | 0

Answered
How to: write .xls into a dynamic folder name ?
folder = [Answer{1},' ',Answer{2},' ',num2str(Answer{3})]; if ~exist(folder, 'dir'); mkdir(folder); end filename = 'patient_...

3 days ago | 0

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Answered
How to run continuously
current_state = 0; writeDigitalPin(a,'D2',current_state); while true if readVoltage(a, 'A1') >= 2 if current_s...

3 days ago | 0

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